Class III malocclusion

Definition

1. According to Angle class III molar relationship refers to:

condition where the mesio-buccal cusp of permanent maxillary first molar occluding in the interdental space between the mandibular first and second molars.

Definition

2. According to British standards definition of class III incisor relationship refers to:

lower incisor edge occludes anterior to the cingulum plateau of the upper incisors.

Etiology

Heredity

Age linked

Functional factor and soft tissue

- tongue posture

- enlarged tonsils and naso-respiratory difficulties.

- excessive epi pharyngeal lymphoid tissue

occlusal forces created by abnormal eruption.

premature loss of deciduous molars.

lack of eruption of maxillary buccal segments.

cleft lip and palate.

compulsive habits of protruding the mandible.

trauma to the mid face during growth phase.

A 25 y/o female patient with c/o of an unesthetic facial and dental appearance

Lateral view of the patient’s face shows prominent lower jaw with the concave profile. Intra orally the molars, canine and incisor relationship is class III with a reverse overjet of 5mm. Mild crowding of upper and lower anterior teeth is present.

Skeletal malocclusion

Discrepancy in shape, size or position of one or both jaws

Dental malocclusion

Discrepancy in shape, size or position of tooth.

Skeletal features

Retrognathic maxilla (short maxilla)

Prognathic mandible (long mandible)

Combination

Intraoral

1. Reverse overjet

2. Unilateral or bilateral posterior crossbite (due to constricted maxillary or more forward positioned mandible)

3. Class III molar and canine relationship

Extraoral

Long face Concave profile Anterior facial divergence

Prominent chin Steep mandibular plane angle (FMA)

References

Laura Mitchell, An Introduction to Orthodontics 3rd edition.

S.I. Bhalaji, Orthodontics The Art and Sciences.